1. Field of the Invention
This invention relates to a voice converter which is suitably used in, for example, a karaoke apparatus.
2. Background
In the field of a karaoke apparatus or the like, recently, many kinds of voice converting techniques in which a process such as frequency conversion is applied to an input voice to produce various effects, have been developed. For example, known are techniques in which the interval of an input voice is shifted by predetermined degrees and the resulting voice is added to the original voice, thereby attaining a so-called harmony effect, and in which a voice of a male is converted into that of a female by shifting an input voice toward higher frequencies by one octave or shifting the formant (the resonance frequency of the vocal tract).
In the voice conversion of the prior art, usually, only a pitch shift or a formant shift is conducted on an input voice so that the formant is merely shifted toward a higher or lower frequency on the frequency axis. Depending on the frequency characteristics of input voices (i.e., the voice quality), therefore, the voice conversion is appropriately conducted, or it is not appropriately conducted, for example, the volume is extremely reduced as a result of the conversion, or an unnatural voice is obtained. Namely, the conversion has a problem in that the result of the conversion is not uniform. The conversion has a further problem in that the range in which the conversion is enabled is restricted to a very narrow one by such nonuniformities.